1. Field of the Invention
This invention pertains to polymers that are useful in cosmetic preparations, particularly to cationic cellulose derivatives of controlled charge density that are useful in hair care preparations.
2. Description of Related Art
Naturally-occurring polymers such as tragacanth, arabic, or karaya gums were used in early hair fixative products. These fixatives were typically delivered from either an aqueous or a hydroalcoholic medium onto damp hair. The hair was then styled and allowed to dry on rollers. This type of product was insufficient for all hairstyles, and an improved, quick drying product was developed, commonly known as hair spray.
Shellac was the first polymer used in hair sprays. Difficulties with shellac led to the use of synthetic resins instead--for example, polyvinylpyrrolidone (PVP), dimethylhydantoin formaldehyde (DMHF), PVP-vinyl acetate copolymer (PVP-VA), and polyvinylpyrrolidone-methylmethacrylate-methacrylic acid terpolymer. Ongoing efforts in the cosmetics industry to synthesize new polymeric resins have been driven by consumer demand for fixative products that are resistant to humidity, but that still may be removed easily upon shampooing.
The use of chlorofluorocarbons in hairsprays has been banned in the United States since 1979. Many hair fixatives are currently applied in a volatile organic compound ("VOC") carrier. As the use of VOC's becomes more restricted, there is an unfilled need for hair fixatives that may be applied with little or no VOC's. It would be desirable to devise a system in which water could replace some or all of the alcohol or propellant that is used in current formulations. Such a substitution presents a similar challenge to that faced by formulators over fifty years ago: how to produce a quick-drying fixative product that is resistant to humidity and that may be easily removed in an aqueous solution (e.g., shampoo). One way in which volatile solvents could be completely or partially replaced would be to use a water-soluble product whose affinity for hair exceeds its affinity for the aqueous solvent in which it is applied.
The principal component of hair is a protein called keratin. Three important factors in determining the binding of a polymer to keratin are: (1) the affinity of the polymer for keratin, (2) the strength of interactions of the polymer with the solvent phase, and (3) the diffusibility of the polymer into the hair. Polymer-keratin affinity is influenced by polymer charge, molecular size, isoelectric point of the hair, pH of the surrounding medium, formulation composition, and substituents attached to the surface of the keratin. The hydrophilicity or hydrophobicity of the polymer affects binding interactions with the aqueous phase. Difflusion into the fiber is controlled by the molecular size of the polymer, pH, reaction temperature, and the past history of the keratin (hysteresis).
Adsorption of a polymer onto keratin may be charge driven or hydrophobically driven. The adsorption process is a continuum between these two pathways, and can vary with changes in the pH or in the polymer structure. At low pH (pH&lt;3.6), the adsorption of cationic polymers is hydrophobically driven as the pH is near or below the isoelectric point of hair. As pH increases above 3.6, the adsorption process becomes charge-driven as the negative charge of the hair fiber increases with increasing pH.
Bonding between polymers and keratin falls into three principal types: primary valence bonds (both ionic and covalent), polar interactions (especially hydrogen bonding), and van der Waals attractions. Cationic polymers in particular primarily bind to keratin through ionic bonds, enhanced by van der Waals forces. The strength of van der Waals bonding may approach that of ionic bonding, as the sum of individual van der Waals interactions increases with the number of repeat units in the polymer.
Polymeric quaternary ammonium salts ("polyquats") have been used for several purposes in cosmetic formulations due to their solubility in both aqueous and aqueous-alcoholic media. Polyquats have been used as thickeners, emulsifiers, fixatives, film formers, and additives in formulations to improve combing of hair, manageability, body, curl retention, and binding to keratin. Cationic ingredients tend to bind to hair keratin due to the low isoelectric point of hair (pH=3.67).
Prior polyquaternary ammonium cellulosic derivatives typically have a low degree of desorption from keratin, resulting in "buildup" or soiling of hair, and they can be resistant to removal by anionic surfactants. These problems have limited their use. Prior polyquaternary ammonium cellulosic derivatives have had low solubility in water, requiring the use of high levels of volatile organic compounds in many hair formulations. Current environmental regulations require the reduction of volatile organic compounds, making the long-term use of prior polyquaternary ammonium cellulosic derivatives impractical for many applications.
Cellulose. Cellulose, a major component of most terrestrial plants, is a polymer formed of repeating .beta.-1,4 D-glucose units ("anhydroglucose units"). Numerous hydroxyl groups on cellulose participate in extensive intra- and inter-molecular hydrogen bonding, making cellulose a stiff, rod-like polymer. Reactions with cellulose generally require initial activation of the hydroxyl groups to enhance nucleophilicity.
The applications and properties of cellulose derivatives are greatly influenced by the degree of substitution along the cellulose chain. The "degree of substitution" is defined as the average number of hydroxyl groups that have been substituted per anhydroglucose unit in the polymeric backbone. Each anhydroglucose unit has three hydroxyl groups, located at the C2, C3, C6 positions. The C2 and C3 positions are secondary alcohols, and C6 is a primary alcohol. The three hydroxyl groups exhibit different rates of reactivity to different reagents. In an etherification reaction, the order of reactivity is C2&gt;C6&gt;C3.
Cellulose ethers are generally soluble in water or common organic solvents. They can be prepared by nucleophilic substitution reactions under alkaline conditions. The most important commercially available cellulose ethers, such as carboxymethyl cellulose (CMC), methylcellulose (MC), hydroxyethyl cellulose (HEC), and hydroxypropyl cellulose (HPC) are prepared by this method. The Michael addition is used to prepare cyanoethylated cellulose or carbamoyl cellulose by treating cellulose with acrylonitrile or acrylamide, respectively. Cellulose ethers are used as thickeners, flow control agents, suspending agents, protective colloids, films, and thermoplastics. Cellulose ethers are generally nontoxic to humans, animals, and ecological systems.
Amino Cellulose Derivatives The introduction of amino groups onto cellulose molecules increases reactivity by forming a cellulosate "macroinitiator" that is suitable for further derivatisation. Amino cellulosics have been used as immunoadsorbents, in enzyme immobilization, as ion-exchange resins, and as macroinitiators for vinyl monomers.
The preparation of primary aminoalkyl cellulosics generally involves reacting activated cellulose with aminoalkyl halides, aminoalkylsulfuric acid, or ethylenimine. Another method to prepare aminoalkyl cellulosics involves the direct reduction of the nitrile group of cyanoethylated cellulose to give aminopropyl cellulose. The Hofmann rearrangement of carbamoylethylcellulose with Br.sub.2 /NaOH for 30-120 min also gives aminopropyl cellulose. Reacting activated cellulose with epichlorohydrin, followed by subsequent reaction with various diamines gives O-[2-Hydroxy-3-(.omega.-aminoalkylamino) propyl cellulose. Cellulose acetate may be treated with sodium naphthalene in tetrahydrofuran to prepare the sodium cellulosate initiator. The sodium cellulosate initiator can then react with the N-carboxy anhydride derivative of D,L phenylalanine, .gamma.-benzyl-L-glutamate, s-benzyl-L-cysteine, or sarcosine to yield single aminoacid cellulose derivatives, without forming polypeptide graft copolymers.
Aminocarbamoyl Cellulosics. A water soluble 2-aminoethyl-carbamoyl cellulose with a low degree substitution (DS.ltoreq.0.02) may be prepared by treating sodium carboxymethyl cellulose with excess ethylenediamine in the presence of water soluble carbodiimides.
Converting carboxymethyl cellulose to an alkyl ester produces a derivative more receptive to aminolysis, thus increasing the degree of substitution. For example, reacting carboxymethyl cellulose ("CMC") (DS&gt;0.1) with methyl chloride at 100.degree. C. yields methyl carboxymethylcellulose ester. Reacting this ester with various diamines in methanol at 150.degree. C. for 1 hour yields aminoamide cellulosics. The aminoamide cellulosics may be quaternized by treatment with methylchloride in methanol at room temperature. The quaternized derivatives had a degree of substitution of 0.67. Betainized cellulose derivatives are prepared after treating the aminoamide cellulosics with Cl(CH.sub.2).sub.y CO.sub.2 Na in isopropanol at 60.degree. C. for 6 hours. The quaternized and betainized cellulosics (DS=0.63) can be applied as hair bleaches and shampoos.
Hydroxyethylcellulose was treated with the betainization reagent prepared by heating a mixture of dimethylglycine, isopropanol, and epichlorohydrin at 50.degree. C. The betainized cellulose improved the feel and combing capacity of hair. The CMC ester may be prepared by treating the CMC salt (DS=1) with dimethylsulfate in isopropanol at 25.degree. C. for 2 hours and 70.degree. C. for 2 hours. The CMC ester is treated with various diamines in toluene at 100.degree. C. for 5 hours, giving aminoamides with a DS of 0.7. The quaternized derivatives have been used to flocculate china clay suspensions.
U.S. Pat. No. 4,988,806 discloses certain aminoalkylcarbamoylmethyl cellulosics, certain monoquaternary ammoniumalkylcarbamoylmethyl cellulosics, and their use in cosmetic preparations.
U.S. Pat. No. 4,415,552 discloses aminoalkylcarbamoylmethyl cellulosics said to be useful as non-immunogenic carriers for allergenic haptens, to help establish immunological tolerance to those haptens. See also Chem. Abstracts 97:203224b (1982).
D. Culberson et al., "Approaches to the Synthesis of Aminoalkylcarbamoyl Cellulosics," Polym. Preprints, vol. 34, no. 1, pp. 564-565 (1993); and D. Culberson et al., "Synthesis and Characterization of Aminoalkylcarbamoyl Cellulosics," Polym. Mat. Sci., vol. 71, pp. 498-499 (1994) disclose the synthesis and characterization of aminopropyl amidocarboxyethyl cellulose, certain aminoalkyl carboxyamidomethyl celluloses, and certain poly quaternary ammonium salts.
D. Culberson et al., "A Study of the Complexation of Alkyl Sulfate Surfactants with Aminoalkylcarbamoyl Cellulosics," printed abstract and copy of slides given at oral presentation, Am. Chem. Soc. Meeting, Anaheim, Calif. (April 1995) discloses phase diagrams of mixtures of aqueous surfactants with certain aminoalkylcarbamoyl cellulosics.
M. Manuszak-Guerrini et al., "A Study of the Complexation of Aminoalkylcarbamoyl Cellulosics and Oppositely Charged Mixed Micelles," preprint of oral presentation, Society of Cosmetic Chemists National Meeting, New York, pp. 57-59 (December 1995) discloses measurements on the interaction of certain aminoalkylcarbamoyl graft copolymers with sodium dodecyl sulfate-octoxynol mixed micelles. See also M. Manuszak-Guerrini et al., "Structure Elucidation of Complexes of Aminoalkylcarbamoyl Cellulosics and Oppositely Charged Mixed Micelles," preprint of poster presentation submitted for Am. Chem. Soc. Mtg., New Orleans, Louis. (Mar. 24-27, 1996).
D. Culberson, "Synthesis and Characterization of Aminoalkylcarbamoyl Cellulosics," pp. 7-53, and 139-146, PhD Dissertation, Louisiana State University, Baton Rouge, Louis. (May 1995) discloses the synthesis and characterization of a number of aminoalkylcarbamoyl cellulosics.
Certain polysaccharide derivatives for use in hair, cosmetic, and flocculating compositions are disclosed in Chem. Abstracts 113:29109e (1989); Chem. Abstracts 112: 160864u (1989); Chem. Abstracts 112:200955h (1989); and Chem. Abstracts 115:282370n (1991).